Electrolytic capacitors are increasingly being used in the design of circuits due to their volumetric efficiency, reliability, and process compatibility. Electrolytic capacitors typically have a larger capacitance per unit volume than certain other types of capacitors, making them valuable in relatively high-current and low-frequency electrical circuits. One type of capacitor that has been developed is a wet electrolytic capacitor that includes an anode, a cathode current collector (e.g., aluminum can), and a liquid or “wet” electrolyte. Wet electrolytic capacitors tend to offer a good combination of high capacitance with low leakage current and a low dissipation factor. In certain situations, wet electrolytic capacitors may exhibit advantages over solid electrolytic capacitors. For example, wet electrolytic capacitors may operate at a higher working voltage than solid electrolytic capacitors. Additionally, wet electrolytic capacitors are often larger in size than solid electrolytic capacitors, leading to larger capacitance values. Unfortunately, however, many conventional capacitors experience significant problems when used with corrosive electrolytes, such as sulfuric acid. For example, aluminum current collectors are highly sensitive to corrosion and are not generally compatible with corrosive electrolytes. Also, under certain conditions (e.g., high temperatures), coatings applied to cathode current collectors (e.g., ruthenium oxide) may become detached due to corrosion by the electrolyte. To avoid these problems, more neutral liquid electrolytes may be employed, but this often results in a corresponding sacrifice in electrical properties.
As such, a need currently exists for a wet electrolytic capacitor that is able to adequately function with a wide variety of electrolytes.